1. Field of the Invention
This invention relates generally to the field of sport balls, such as tennis balls. More particularly, the invention comprises the combination of a container for a plurality of sport balls with a device for testing the playing condition of the balls.
2. Background
Tennis balls and certain other types of sport balls, such as racquet balls and handballs, are manufactured with a predetermined internal pressure, which imparts resiliency. The pressure is retained within a sphere of elastomeric material; however, the material is not perfectly impermeable. The internal pressure diminishes over time and with extended play. As the pressure diminishes, so does the resiliency of the ball, which has a deleterious effect on the playing characteristics of the ball.
Official organizations for tennis and other sports have established specifications for the balls used to play the respective sports. For example, the International Tennis Federation (ITF) Rules of Tennis specify that the ball shall have a bound of more than 53 inches and less than 58 inches when dropped 100 inches upon a concrete base. The Rules also specify that the forward and return deformation of the ball when placed under a load of 18 pounds shall be between 0.220 inch and 0.290 inch. Both of these specifications relate to the resiliency of the ball and hence to its playing characteristics. Recreational players are generally not concerned with whether or not a particular ball meets the precise specifications of an official organization. Such players are more concerned with the general playability of a ball and will often test a ball by squeezing it by hand or bouncing it on pavement. These informal tests are highly subjective. A number of devices have been proposed for objectively testing sport balls, particularly tennis balls. Such devices are shown, for example, in U.S. Pat. Nos. 5,222,391; 5,245,862; 5,291,774; 5,511,410; 5,567,870; 5,639,969; and 5,760,312.
Some of the prior art testing devices shown in the above-mentioned patents are intended for laboratory use, while others are intended to be used by individual players. However, all of the known prior art devices are relatively complex and, therefore, relatively expensive. Many of the devices have electronic components and all have one or more moving parts. There remains a perceived need for an inexpensive ball tester that can be provided to consumers at the time that the balls are purchased, analogous to the way that many dry cell batteries are sold with integral devices for testing the condition of the battery. Preferably, such a device would be simple to use and would be incorporated into the package in which balls are sold and stored so that the player would not be burdened with the inconvenience and weight of an additional item to carry.
The present invention provides a device for testing the playing condition of sport balls. The invention is preferably configured as the testing device in combination with a container for storing the sport balls; however, the invention may also be configured as a stand-alone testing device. A cylindrical container for the sport balls has a removable end cap that may be attached to the closed end of the container. A ball placed within the end cap is subjected to predetermined compression when the end cap is secured onto the container. A pressure indicator in the end cap provides a visual indication of the internal pressure in the ball, and hence, one important measure of the playing condition of the ball.